Suppying an output voltage using unsynchronized direct current to direct current converters

ABSTRACT

A system that may include a first direct current to direct current (DC) converter that is arranged to determine at a first determination rate whether to alter a parameter of operation of the first DC to DC converter and to selectively alter the parameter of operation of operation of the first DC to DC converter in response to the determination; and a second switched-mode DC to DC converter that is arranged to determine at a second determination rate whether to alter the parameter of operation of the second DC to DC converter and to selectively alter the parameter of operation of operation of the second DC to DC converter in response to the determination. The second determination rate is higher by at least a factor of two than the first determination rate. The first and second DC to DC converters are mutually unsynchronized.

RELATED APPLICATIONS

This application claims priority from U.S. provisional patent Ser. No.61/678,676 having a filing date of Aug. 2, 2012 which is incorporated byreference.

BACKGROUND OF THE INVENTION

A direct current (DC) to direct current (DC) converter converts a sourceof direct current (DC) from one voltage level to another. Whenconverting an input voltage to a higher level the circuit is called a“boost” or step-up converter, and when converting into a lower level itis called a “buck” or step-down converter.

There are several types of DC to DC converters. One known DC to DCconverter is a switched-mode DC to DC converter that converts DC voltageof a first level from a DC power supply by controlling a switch that maybe closed to selectively allow the provision of input power (from the DCpower supply) to storing the input energy temporarily in an energystorage component (such as an inductor and/or a capacitor) that releasesthat energy to the output of the DC to DC converter at a differentlevel.

FIG. 1

FIG. 1 illustrates a prior art DC-DC converter 10. It includes DC powersupply 11, switch 12, diode 13, inductor 14, capacitor 15, output ports16, measurement circuit (such as voltmeter 17) and controller 18. Thecontroller 18 controls the switch 12 in response to the value of outputvoltage Vo. DC to DC converter 10 is connected to a load 20.

FIG. 2

FIG. 2 illustrates some waveforms generated during the operation of DCto DC converter 10.

The switch 12 is kept closed during switch ON times (T_(ON) 21 of FIG.2) and this causes the inductor 14 to experience a forward voltage dropV_(L)=V_(i)−V_(O) (as illustrates by graph 23) which causes the inductor14 to be charged with energy (from power supply 11) and the current onthe inductor 14 increases linearly (graph 24) assuming the inductor 14does not reach saturation.

The switch 12 is opened during switch OFF times (T_(OFF) 22 of FIG. 2)and this causes diode 13 to conduct and thus the voltage drop V_(L) oninductor 14 is negative V_(L)=V_(D)−V_(O). During this time period theinductor's energy keeps a flow of current into the load 20, but thiscurrent decreases linearly as well (graph 24).

The average current the buck circuit can provide to the output load isshown in the diagram as I_(AVG) 25. Adjusting the circuit parameterssuch as duty cycle and frequency of the switch 12 may change theavailable current to the output load. If the average output load issmaller than this average current then voltage will increase beyondrequired level and it will fall below it when the output load issmaller. For this reason, in order to keep a constant output voltagelevel a closed loop mechanism is typically implemented.

Closed Loop Mechanism.

A popular way of implementing a closed loop mechanism for keeping astable output voltage level is by using “ON-OFF switching” mechanism.The average inductor current I_(AVG) 25 is higher than the average loadcurrent I_(load) causing the output voltage V_(O) to increase when theswitching mechanism is on.

The output voltage Vo is sensed by the circuit and when voltage risesabove a certain threshold the switching mechanism is stopped allowingthe voltage to drop as a result of the output load. This is referred toas “Inactive Period” (Denoted 32 in FIG. 3). After the output voltagedrops below a certain threshold the switching mechanism is turned onagain. This is referred to as “Active Period” (denoted 31 in FIG. 3).

FIG. 3

Prior art waveforms related to the activation of a prior art switchedmode DC to DC converter are illustrated in FIG. 3. For simplicity theoutput load is shown as constant.

The output voltage (Vo) 34 exhibits ripples that result from severalfactors in the system such as the hysteresis of the voltage thresholddetection mechanism, the difference between I_(AVG) and I_(LOAD) andswitching frequency.

One way of reducing output ripple is to adjust the duty cycle of theswitch control in order to reduce the difference between these currentsand reduce the slope of V_(O). When the average output current duringT_(ON) is lower than the average load current then the load is instarvation and the converter cannot meet the load demand. In this casethe output voltage will fall below its target.

In many electronic systems there is a dedicated ASIC component that isresponsible for providing power to the different consumers. Thiscomponent is referred to as Power Management Unit (PMU). As designsbecome more advanced the typical consumer requires increasingly largercurrent form the system. A typical PMU in portable application systemshas several voltage converters (DC-DC modules) that convert batteryvoltage to different voltage levels to meet the system power demands.

As mentioned above, a given DC-DC converter can provide a certain amountof current to the load. If load is larger than the maximum averagecurrent the circuit can provide the consumer will be in starvation. Inthis case the closed loop mechanism will be in “Active” mode constantly.

Traditionally, if the PMU does not have a single DC-DC converter thatcan meet the demand of a consumer then an external component must bepurchased and integrated into the system, increasing the system cost andprinted circuit board (PCB) area.

Even though the PMU may have several different DC-DC converters that thesum of their available current is enough to meet the consumer demand itis not possible to simply connect them together to supply the demand.Several tests in the lab show that this can lead to output voltageinstability, decreased efficiency and might cause damage to the PMU.

Some PMUs can solve this issue by synchronizing the control signals ofseveral DC-DC converters, effectively joining them together into one bigDC-DC converter with the combined size of the switches and inductorcomponents. This, however, requires additional logic that increases costof the PMU, and might not be available in any given PMU component.

FIG. 4

FIG. 4 illustrates typical prior art waveforms 41, 42, 43, 44, 45, 47and 48 generated in relation to a scenario in which a load may be in astate of starvation (lack of current illustrated by regions 46). Thecurrent (44) supplied by the DC to DC converter to the load is notenough to provide the demand from the load (45). As a result the voltageVo (42) starts to drop below the desired voltage level Vtarget (41)during the OFF period of the switch T_(OFF) when I_(AVG) falls belowI_(LOAD)—as illustrated by areas 44. Graph 47 illustrates a switchcontrol signal (“switch state”) that toggles the switch of the DC to DCconverter and also illustrates an ON_CTL signal (48) that shows that theswitch is toggled during the entire duration.

Avoiding Oscillation on Output Voltage

Traditionally, there is a risk that two different DC to DC convertersthat are controlled by separate controllers and are coupled in parallelto each other (to provide the same output voltage) might cause theoutput voltage to oscillate.

This is the reason that traditionally using several DC-DC converters inparallel requires synchronization of the switching elements of each DCto DC converter, which complicates the design of the DC to DC convertersand increases the overall cost.

FIG. 5

FIG. 5 illustrates various waveforms generated when using two DC-DCconverters with close frequencies and similar current rating.

During time periods 52 the output voltage 53 is below the voltagethreshold low hysteresis level, and during periods 51 the output voltageis above the high hysteresis level. The low hysteresis level is slightlybelow Vtarget and the high hysteresis level is slightly above Vtarget.

In each rising edge of the respective DC-DC converter a switchingoperation occurs if the output voltage is below the low hysteresis point(periods 51) and stops if it is above the high point (periods 52).

The bandwidth of a DC-DC converter is limited by the frequency of theswitching. The decision point whether to close the switch comes usuallyat the beginning of each switch period.

The diagram shows output voltage instability (large Vo fluctuations) dueto the fact that both controllers might decide to perform a switch inthe same time while the current that is transferred to the output is asum of both of them. Graphs 54, 55, 56, 57, 58, 59 and 59′ represent thecurrent drained from a first DC to DC converter, the load current, thecurrent drained from a second DC to DC converter, a first switch statecontrol signal, a control signal that determines whether to toggle thefirst switch, a second switch state control signal, and control signalthat determines whether to toggle the switch first switch, respectively.

There is a need to provide an efficient system and method for operatingmultiple DC to DC converters.

SUMMARY

According to an embodiment of the invention there may be provided asystem that may include: (i) a first switched-mode direct current todirect current (DC) converter that is arranged to selectively toggle afirst switch at a first switching rate; wherein the first switch iscoupled between a first power supply and energy storage components ofthe first DC to DC converter; a second switched-mode DC to DC converterthat is arranged to selectively toggle a second switch at a secondswitching rate; wherein the second switch is coupled between a secondpower supply and energy storage components of the second DC to DCconverter; wherein the second switching rate is higher by at least afactor of two than the first switching rate; and wherein the first andsecond switched-mode DC to DC converters are mutually unsynchronized.

According to an embodiment of the invention there may be provided amethod for providing an output voltage to a load, the method mayinclude: (i) for each cycle of operation of a first direct current (DC)to DC converter: (i.1) toggling a first switch at a first switching rateduring the cycle of operation of the first DC to DC converter if at acertain point in the cycle of operation of the first DC to DC converterthe output voltage is below a third voltage threshold; wherein the firstswitch is coupled between a first power supply and energy storagecomponents of the first DC to DC converter; (i.2) maintaining, by thefirst DC to DC converter the first switch open if at the certain pointin the cycle of operation of the first DC to DC converter the outputvoltage is above a fourth voltage threshold; (ii) for each cycle ofoperation of a second DC to DC converter: (ii.1) toggling a secondswitch at a second switching rate during the cycle of operation of thesecond DC to DC converter if at a certain point in the cycle ofoperation of the second DC to DC converter the output voltage is below afirst voltage threshold; wherein the second switch is coupled between asecond power supply and at least one energy storage components of thesecond DC to DC converter; (ii.2) maintaining, by the second DC to DCconverter the second switch open if at the certain point in the cycle ofoperation of the second DC to DC converter the output voltage is above asecond voltage threshold; wherein the second switching rate is higher byat least a factor of two than the first switching rate; and wherein thefirst and second switched-mode DC to DC converters are coupled inparallel to each other and are mutually unsynchronized.

According to an embodiment of the invention there is provided a systemthat includes a first direct current to direct current (DC) converterthat is arranged to determine at a first determination rate whether toalter a parameter of operation of the first DC to DC converter and toselectively alter the parameter of operation of operation of the firstDC to DC converter in response to the determination; a secondswitched-mode DC to DC converter that is arranged to determine at asecond determination rate whether to alter the parameter of operation ofthe second DC to DC converter and to selectively alter the parameter ofoperation of operation of the second DC to DC converter in response tothe determination; wherein the second determination rate is higher by atleast a factor of two than the first determination rate; and wherein thefirst and second DC to DC converters are mutually unsynchronized.

The second determination rate (rate in which the DC to DC converterdetermines whether to change a parameter) is higher than the firstdetermination rate. The second determination rate may be higher than thefirst determination rate by a degree that will reduce the output voltageripple. It may be higher by a factor of 2, 3, 4, 5 and more. The factormay be a positive integer but can also be a non-integer number. It isexpected that an increase of the ratio will result in lower outputvoltage oscillation.

The parameter of operation may be a switching rate, a duty cycle, or anyparameter that may affect the provision of the output voltage.

According to an embodiment of the invention there is provided a methodfor providing an output voltage to a load, the method may include:determining, by a first direct current (DC) to DC converter, at a firstdetermination rate whether to alter a parameter of operation of thefirst DC to DC converter; selectively altering the parameter ofoperation of operation of the first DC to DC converter in response tothe determination; determining, by a second direct current (DC) to DCconverter, at a second determination rate whether to alter a parameterof operation of the second DC to DC converter; selectively altering theparameter of operation of operation of the second DC to DC converter inresponse to the determination; wherein the second determination rate ishigher by at least a factor of two than the first determination rate;and wherein the first and second DC to DC converters are coupled inparallel to each other and are mutually unsynchronized.

BRIEF DESCRIPTION OF THE DRAWINGS

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings in which:

FIG. 1 illustrates a prior art DC to DC converter;

FIG. 2 illustrates prior art waveforms;

FIG. 3 illustrates prior art waveforms;

FIG. 4 illustrates prior art waveforms;

FIG. 5 illustrates prior art waveforms;

FIG. 6 illustrates waveforms according to an embodiment of theinvention;

FIG. 7 illustrates waveforms according to an embodiment of theinvention;

FIG. 8 illustrates a device according to an embodiment of the invention;

FIG. 9 illustrates a device according to an embodiment of the invention;

FIG. 10 illustrates a method according to an embodiment of theinvention; and

FIG. 11 illustrates a method according to an embodiment of theinvention.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

DETAILED DESCRIPTION OF THE DRAWINGS

In the following detailed description, numerous specific details are setforth in order to provide a thorough understanding of the invention.However, it will be understood by those skilled in the art that thepresent invention may be practiced without these specific details. Inother instances, well-known methods, procedures, and components have notbeen described in detail so as not to obscure the present invention.

The subject matter regarded as the invention is particularly pointed outand distinctly claimed in the concluding portion of the specification.The invention, however, both as to organization and method of operation,together with objects, features, and advantages thereof, may best beunderstood by reference to the following detailed description when readwith the accompanying drawings.

It will be appreciated that for simplicity and clarity of illustration,elements shown in the figures have not necessarily been drawn to scale.For example, the dimensions of some of the elements may be exaggeratedrelative to other elements for clarity. Further, where consideredappropriate, reference numerals may be repeated among the figures toindicate corresponding or analogous elements.

Because the illustrated embodiments of the present invention may for themost part, be implemented using electronic components and circuits knownto those skilled in the art, details will not be explained in anygreater extent than that considered necessary as illustrated above, forthe understanding and appreciation of the underlying concepts of thepresent invention and in order not to obfuscate or distract from theteachings of the present invention.

Any reference in the specification to a method should be applied mutatismutandis to a system capable of executing the method.

Any reference in the specification to a system should be applied mutatismutandis to a method that may be executed by the system.

Although the following examples refer to switched-mode DC to DCconverters it is applicable to other types of DC to DC converters.

There is provided a system and a method. The system includes multipleswitched mode DC to DC converters wherein the switching rates ofdifferent switched mode DC to DC converters differ from each other by atleast two (especially—by at least five).

For each pair of switched mode DC to DC converters one switched mode DCto DC converter will be a fast switched mode DC to DC converter and theother will be a slow switched mode DC to DC converter. The fast switchedmode DC to DC converter reacts much faster to changes in the outputvoltage and/or output current (faster in relation to the slow switchedmode DC to DC converter). The fast switched mode DC to DC converterswitches to inactive state as soon as the voltage starts to increase,and by this avoiding oscillation.

The switching frequencies of switched mode DC to DC converters may befar apart from each other in a way that a fast switched mode DC to DCconverter sees the slower switched mode DC to DC converter as providingDC. It has been shown that a ratio of five between the switching ratesof the switched mode DC to DC converters gives good performance.

Each switched mode DC to DC converter may have over-current protectioncircuits that will limit the current it can output. For example, theduty cycle of each switched mode DC to DC converter may be limited in away that prevents damage to the internal switching elements of theinductor when the switched mode DC to DC converter provides its maximumcurrent.

When a current required by the load exceeds a certain level (that ischaracteristic of the first DC to DC converter) the output voltagestarts to drop. As a result the fast switched mode DC to DC converterenters an ACTIVE mode and starts to toggle its switch. The added currentfrom the fast switched mode DC to DC converter ensures that the currentprovided by the system is higher than I_(LOAD) and as a result theoutput voltage remains stable.

In order to minimize output voltage ripple, voltage threshold levels ofdifferent switched mode DC to DC converters may be similar to eachother. Small inaccuracy of voltage levels between the switched mode DCto DC converters may increase output ripple.

FIG. 8

FIG. 8 illustrates system 200 according to an embodiment of theinvention.

System 200 may be an integrated circuit, a power management module, achip set, a mobile device, a computer and the like.

System 200 includes:

-   -   a. A first switched-mode direct current to direct current (DC)        converter 210 that is arranged to selectively toggle a first        switch 212 at a first switching rate. The first switch 212 is        coupled between a first power supply 211 and one or more energy        storage components 213 of the first DC to DC converter (the        energy storage components may be an inductor and a capacitor).        The one or more energy storage components are coupled to a first        output port 216 to provide an output voltage. The first switched        mode DC to DC converter also has a first controller 218 that is        connected to a first voltmeter 217 and controls the first switch        212.    -   b. A second switched-mode DC to DC converter 310 that is        arranged to selectively toggle a second switch 312 at a second        switching rate. The second switch 312 is coupled between a        second power supply 311 and one or more energy storage        components 313 of the second DC to DC converter 310. The one or        more energy storage components 313 are coupled to a second        output port 316 to provide an output voltage. The second        switched mode DC to DC converter also has a second controller        318 that is connected to a second voltmeter 317 and controls the        second switch 312.

The first and second switched-mode DC to DC converters 210 and 310 aremutually unsynchronized. Each switched mode DC to DC converter (out of210 and 310) operates in a cyclic manner and these cycles are notsynchronized. At a certain time of each cycle (for example—the beginningof each cycle) each DC to DC converter decided whether to toggle itsswitch (if it should supply voltage) or not.

Reference number 76 of FIGS. 6 and 7 illustrates the beginning of cyclesof the first switched mode DC to DC converter and reference numbers72(1)-72(35) of FIGS. 6 and 7 illustrates the beginning of cycles of thesecond switched mode DC to DC converter. These points of time can betime shifted from each other but may occasionally overlap.

Each of the first and second switched mode DC to DC converters 210 and310 can equal (or at least resemble) DC to DC converter 10 of FIG. 1.

The first switched mode DC to DC converter 210 has a first output port216 and the second switched mode DC to DC converter 310 has a secondoutput port 316. These output ports 216 and 316 can be connected inparallel to each other by coupling elements 202 that may belong tosystem 200 (as illustrated in FIG. 8) or not belong to system 200 (forexample—if system 200 is an integrated circuit and the coupling elements202 are conductors of a printed circuit board (PCB) coupled to theintegrated circuit. The coupling element 202 provides output voltage Vo206 to load 204.

The second switching rate is higher than the first switching rate. Thesecond switching rate may be higher than the first switching rate by adegree that will reduce the output voltage ripple. It may be higher by afactor of 2, 3, 4, 5 and more. The factor may be a positive integer butcan also be a non-integer number. It is expected that an increase of theratio will result in lower output voltage oscillation.

The difference between the first and second switching rates may allowthe first switched mode DC to DC converter 210 to supply voltage to theload virtually regardless of the second switched mode DC to DC converter310 and allow the second switched mode DC to DC converter 310 to supplyvoltage only when the supply of power by the first switched mode DC toDC converter 210 is not enough—and the load may enter a starvation.

At a certain time of each cycle of the first switched mode DC to DCconverter, the first switched mode DC to DC converter 210 determineswhether to (i) enter an ACTIVE mode (and to toggle the first switch 212at the first switching rate) or (ii) leave its first switch open duringthe entire cycle (this may involve entering an INACTIVE mode).

The determination includes comparing output voltage Vo 206 to a thirdvoltage threshold TH3. If Vo is lower than TH3 than the first switchedmode DC to DC converter 210 enters the ACTIVE mode. If Vo exceeds afourth voltage threshold TH4—it leaves its first switch open during theentire cycle (enters or stays in INACTIVE mode).

TH3 may equal TH4 or may differ from TH4. TH4 may be higher than TH3 toprovide a hysteresis loop.

At a certain time of each cycle of the second switched mode DC to DCconverter, the second switched mode DC to DC converter 310 determineswhether to (i) enter an ACTIVE mode (and to toggle the second switch 312at the second switching rate) or (ii) leave its second switch openduring the entire cycle (this may involve entering an INACTIVE mode).

The determination includes comparing output voltage Vo 206 to a firstvoltage threshold TH1. If Vo is lower than TH1 than the second switchedmode DC to DC converter 210 enters the ACTIVE mode. If Vo exceeds asecond voltage threshold TH2—it leaves its second switch open during theentire cycle.

TH1 may equal TH2 or may differ from TH2. TH2 may be higher than TH1 toprovide a hysteresis loop.

TH1 may equal TH3 or may differ from it. TH2 may equal TH4 or may differfrom it. According to an embodiment of the invention TH1 does not exceedTH3 and additionally or alternatively, TH2 does not exceed TH4.

The operation of switched mode DC to DC converters 210 and 310 will befurther illustrated by FIGS. 6 and 7.

FIG. 6

In FIG. 6 TH1 equals TH3 and both are denoted 62. TH2 equals TH4 andboth are denoted 64.

In FIG. 6 Vo 61 fluctuates (output voltage ripple denoted 75) about atarget voltage Vtarget 63. The ripples are significantly lower thanthose illustrated in FIGS. 4 and 5.

The current 65 supplied by the first DC to DC converter 210 linearlyrises during ACTIVE periods of the first switched mode DC to DCconverter 210 and linearly decreased during INACTIVE periods.

At the beginning (76) of each cycle of the first switched mode DC to DCconverter 210 Vo is lower than TH3 62 and thus the first switched modeDC to DC converter 210 enters an ACTIVE mode—as illustrated by controlsignal 70 (ON_CTL SLOW). The first switch toggles at a first switchingrate—as illustrated by Slow Switch State signal 68. The first switchedmode DC to DC converter 210 enters an INACTIVE mode once Vo exceeds TH464.

At the beginning of cycles 72(8)-72(14) and 72(22)-72(28) of the secondswitched mode DC to DC converter 310 Vo is lower than TH1 62 and thesecond switched mode DC to DC converter 310 enters an ACTIVE mode—asillustrated by control signal 71 (ON_CTL FAST). The second switchtoggles at a second switching rate—as illustrated by Fast Switch Statesignal 69. In the beginning of these cycles Vo lowers to a level thatindicates that the provision of voltage by the first switched mode DC toDC converter 210 is not enough—and that the second switched mode DC toDC converter 310 should assist in the provision of voltage to the load.At the beginning of cycles 72(1)-72(7), 72(15)-72(21) and 72(29)-72(35)of the second switched mode DC to DC converter 310 Vo is higher than TH264 and thus the second switched mode DC to DC converter 310 leave itssecond switch open during the entire cycle—as illustrated by controlsignal 71 (ON_CTL FAST). The second switch does not toggle—asillustrated by Fast Switch State signal 69.

FIG. 7

In FIG. 7 TH1<TH2<TH3<TH4. TH1 is denoted 86, TH2 is denoted 84, TH3 isdenoted 83 and TH4 is denoted 81. Thus—there are two hysteresisloops—one for each switched mode DC to DC converter.

In FIG. 7 Vo 61 fluctuates (output voltage ripple denoted 99). Theripples are significantly lower than those illustrated in FIGS. 4 and 5.

The current 65 supplied by the first DC to DC converter 210 linearlyrises during ACTIVE periods of the first switched mode DC to DCconverter 210 and linearly decreased during INACTIVE periods.

At the beginning (76) of each cycle of the first switched mode DC to DCconverter 210 Vo is smaller than TH3 83 and thus the first switched modeDC to DC converter 210 enters an ACTIVE mode—as illustrated by controlsignal 70 (ON_CTL SLOW). The first switch toggles at a first switchingrate—as illustrated by Slow Switch State signal 68. The first switchedmode DC to DC converter 210 enters an INACTIVE mode once Vo exceeds TH481.

At the beginning of cycles 72(8)-72(13) and 72(20)-72(25) of the secondswitched mode DC to DC converter 310 Vo is lower than TH1 86 and thusthe second switched mode DC to DC converter 310 enters an ACTIVE mode—asillustrated by control signal 71 (ON_CTL FAST). The second switchtoggles at a second switching rate—as illustrated by Fast Switch Statesignal 69.

In the beginning of these cycles Vo lowers to a level that indicatesthat the provision of voltage by the first switched mode DC to DCconverter 210 is not enough—and that the second switched mode DC to DCconverter 310 should assist in the provision of voltage to the load. Thesecond switched mode DC to DC converter 310 enters an INACTIVE mode onceVo exceeds TH2 84.

At the beginning of cycles 72(1)-72(7), 72(14)-72(19) and 72(26)-72(31)of the second switched mode DC to DC converter 310 Vo is higher than TH284 and thus the second switched mode DC to DC converter 310 leave itssecond switch open during the entire cycle—as illustrated by controlsignal 71 (ON_CTL FAST). The second switch does not toggle—asillustrated by Fast Switch State signal 69.

Although the previous text refers to two switched mode DC to DCconverters there can be provide more than two switched DC to DCconverters—and the relationships between these switching rates resemble(in the sense of being different from each other) the ratios between theswitching rates of the first and second switched mode DC to DCconverters.

FIG. 9

FIG. 9 illustrates system 400 according to an embodiment of theinvention.

System 400 includes N Switched Mode DC To DC ConvertersSMDTDC(1)-SMDCTDC(N) 410(1)-410(N), wherein N is an integer that exceedstwo. In FIG. 9 N exceeds three.

SMDTDC(1) 410(1) is a first switched mode DC to DC converter. SMDTDC(2)410(2) is a second switched mode DC to DC converter. And SMDTDC(3)410(3) is a third switched mode DC to DC converter.

Switched mode DC to DC converters SMDTDC(1)-SMDCTDC(N) 410(1)-410(N)have switching rates of SR(1)-SR(N), respectively.

Index n ranges between 1 and N. For each n that exceeds oneSR(n)=SR(n−1)×F(n), wherein F(n) exceeds one (and may exceed 2, 3, 4, 5and even more).

Each one of switched mode DC to DC converters SMDTDC(1)-SMDCTDC(N)410(1)-410(N) may resemble switched mode DC to DC converter 10 of FIG.1.

The n′th switched mode DC to DC converter SMDCTDC(n) 410(n) mayselectively toggle an n′th switch 412(n) at an SN(n) switching rate. Then′th 412(n) is coupled between an n′th power supply 411(n) and one ormore energy storage components 413(n) of the n′th SMDCTDC(n) 410(n). Theone or more energy storage components 413(n) are coupled to an n′thoutput port 416(n) to provide an output voltage. SMDCTDC(n) 410(n) alsohas an n′th controller 418(n) that is connected to an n′th voltmeter417(n) and controls the n′th switch 412(n).

FIG. 9 illustrates the N switched mode DC to DC converters as connectedin parallel to each other via coupling elements 402 to provide outputvoltage 406 to load 404.

FIG. 10

FIG. 10 illustrates method 500 for providing an output voltage to aload, according to an embodiment of the invention.

Method 500 includes a repetitive sequence of operations 510 executed bya first switched mode DC to DC converter and a repetitive sequence ofoperations 520 executed by a second switched mode DC to DC converter.These sequences are executed in an unsynchronized manner.

Sequence 510 is repeated each cycle of operation of the first DC to DCconverter and includes:

-   -   a. Comparing, (512) at a certain point in the cycle of operation        of the first DC to DC converter the output voltage to a third        voltage threshold and to a forth voltage threshold. The        comparison can be done in parallel or in a sequential manner (in        which one or both comparisons are made). The certain point can        be the beginning of the cycle but this is not necessarily so.    -   b. If, according to the comparison, the output voltage is below        a third voltage threshold (at the certain point of time during        the cycle of operation of the first DC to DC converter) then        stage 512 is followed by stage 514 of toggling a first switch at        a first switching rate. The first switch is coupled between a        first power supply and at least one energy storage components of        the first DC to DC converter.    -   c. If, according to the comparison, the output voltage is above        a forth voltage threshold (at the certain point of time during        the cycle of operation of the first DC to DC converter) then        stage 512 is followed by stage 516 of maintaining, by the first        DC to DC converter the first switch open.    -   d. Stages 514 and 516 are followed by stage 512.

Sequence 610 is repeated each cycle of operation of the second DC to DCconverter and includes:

-   -   a. Comparing, (612) at a certain point in the cycle of operation        of the second DC to DC converter the output voltage to a first        voltage threshold and to a second voltage threshold. The        comparison can be done in parallel or in a sequential manner (in        which one or both comparisons are made). The certain point can        be the beginning of the cycle but this is not necessarily so.    -   b. If, according to the comparison, the output voltage is below        a first voltage threshold (at the certain point of time during        the cycle of operation of the second DC to DC converter) then        stage 612 is followed by stage 614 of toggling a second switch        at a second switching rate. The second switch is coupled between        a second power supply and at least one energy storage components        of the second DC to DC converter.    -   c. If, according to the comparison, the output voltage is above        a second voltage threshold (at the certain point of time during        the cycle of operation of the second DC to DC converter) then        stage 612 is followed by stage 616 of maintaining, by the second        DC to DC converter the second switch open.    -   d. Stages 614 and 616 are followed by stage 612.

The second switching rate is higher by at least a factor of two than thefirst switching rate. The first and second switched-mode DC to DCconverters are coupled in parallel to each other and are mutuallyunsynchronized.

FIG. 11 illustrates method 700 according to an embodiment of theinvention.

Method 700 includes two unsynchronized sets of stages. It may start bystages 710 and 760.

Stage 710 may include performing, by a first DC to DC converter, a DC toDC conversion of an input voltage to provide an output voltage—both areDC voltages.

Stage 710 is controlled by stage 720 and 730 that determine the mannerin which the DC to DC conversion occurs—by setting a parameter of the DCto DC conversion of stage 710. The parameter can include . . . [PLEASEADD]

Stage 720 includes determining, by a first direct current (DC) to DCconverter, at a first determination rate whether to alter a parameter ofoperation of the first DC to DC converter. The determination may beresponsive to a value of the output voltage. If it is determined toalter the parameter then stage 720 is followed by stage 730 of alteringthe parameter of operation of operation of the first DC to DC converterin response to the determination. Else—stage 720 is followed by itself.

Stage 720 may include, for example, stage 512 of FIG. 6.

Stage 760 may include performing a DC to DC conversion, by a second DCto DC converter, of an input voltage to provide an output voltage—bothare DC voltages.

Stage 760 is controlled by stage 770 and 780 that determine the mannerin which the DC to DC conversion occurs—by setting a parameter of the DCto DC conversion of stage 760.

Stage 770 includes determining, by a second direct current (DC) to DCconverter, at a second determination rate whether to alter a parameterof operation of the second DC to DC converter. The determination may beresponsive to a value of the output voltage. If it is determined toalter the parameter then stage 770 is followed by stage 780 of alteringthe parameter of operation of operation of the second DC to DC converterin response to the determination. Else—stage 770 is followed by itself.

Stage 770 may include, for example, stage 612 of FIG. 6.

The second determination rate is higher by at least a factor of two thanthe first determination. The first and second DC to DC converters arecoupled in parallel to each other and are mutually unsynchronized.

In the foregoing specification, the invention has been described withreference to specific examples of embodiments of the invention. It will,however, be evident that various modifications and changes may be madetherein without departing from the broader spirit and scope of theinvention as set forth in the appended claims.

Moreover, the terms “front,” “back,” “top,” “bottom,” “over,” “under”and the like in the description and in the claims, if any, are used fordescriptive purposes and not necessarily for describing permanentrelative positions. It is understood that the terms so used areinterchangeable under appropriate circumstances such that theembodiments of the invention described herein are, for example, capableof operation in other orientations than those illustrated or otherwisedescribed herein.

The connections as discussed herein may be any type of connectionsuitable to transfer signals from or to the respective nodes, units ordevices, for example via intermediate devices. Accordingly, unlessimplied or stated otherwise, the connections may for example be directconnections or indirect connections. The connections may be illustratedor described in reference to being a single connection, a plurality ofconnections, unidirectional connections, or bidirectional connections.However, different embodiments may vary the implementation of theconnections. For example, separate unidirectional connections may beused rather than bidirectional connections and vice versa. Also,plurality of connections may be replaced with a single connection thattransfers multiple signals serially or in a time multiplexed manner.Likewise, single connections carrying multiple signals may be separatedout into various different connections carrying subsets of thesesignals. Therefore, many options exist for transferring signals.

Although specific conductivity types or polarity of potentials have beendescribed in the examples, it will be appreciated that conductivitytypes and polarities of potentials may be reversed.

Each signal described herein may be designed as positive or negativelogic. In the case of a negative logic signal, the signal is active lowwhere the logically true state corresponds to a logic level zero. In thecase of a positive logic signal, the signal is active high where thelogically true state corresponds to a logic level one. Note that any ofthe signals described herein may be designed as either negative orpositive logic signals. Therefore, in alternate embodiments, thosesignals described as positive logic signals may be implemented asnegative logic signals, and those signals described as negative logicsignals may be implemented as positive logic signals.

Furthermore, the terms “assert” or “set” and “negate” (or “deassert” or“clear”) are used herein when referring to the rendering of a signal,status bit, or similar apparatus into its logically true or logicallyfalse state, respectively. If the logically true state is a logic levelone, the logically false state is a logic level zero. And if thelogically true state is a logic level zero, the logically false state isa logic level one.

Those skilled in the art will recognize that the boundaries betweenlogic blocks are merely illustrative and that alternative embodimentsmay merge logic blocks or circuit elements or impose an alternatedecomposition of functionality upon various logic blocks or circuitelements. Thus, it is to be understood that the architectures depictedherein are merely exemplary, and that in fact many other architecturesmay be implemented which achieve the same functionality.

Any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality may be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality.

Furthermore, those skilled in the art will recognize that boundariesbetween the above described operations merely illustrative. The multipleoperations may be combined into a single operation, a single operationmay be distributed in additional operations and operations may beexecuted at least partially overlapping in time. Moreover, alternativeembodiments may include multiple instances of a particular operation,and the order of operations may be altered in various other embodiments.

Also for example, in one embodiment, the illustrated examples may beimplemented as circuitry located on a single integrated circuit orwithin a same device. Alternatively, the examples may be implemented asany number of separate integrated circuits or separate devicesinterconnected with each other in a suitable manner.

Also for example, the examples, or portions thereof, may implemented assoft or code representations of physical circuitry or of logicalrepresentations convertible into physical circuitry, such as in ahardware description language of any appropriate type.

However, other modifications, variations and alternatives are alsopossible. The specifications and drawings are, accordingly, to beregarded in an illustrative rather than in a restrictive sense.

In the claims, any reference signs placed between parentheses shall notbe construed as limiting the claim. The word ‘comprising’ does notexclude the presence of other elements or steps then those listed in aclaim. Furthermore, the terms “a” or “an,” as used herein, are definedas one or more than one. Also, the use of introductory phrases such as“at least one” and “one or more” in the claims should not be construedto imply that the introduction of another claim element by theindefinite articles “a” or “an” limits any particular claim containingsuch introduced claim element to inventions containing only one suchelement, even when the same claim includes the introductory phrases “oneor more” or “at least one” and indefinite articles such as “a” or “an.”The same holds true for the use of definite articles. Unless statedotherwise, terms such as “first” and “second” are used to arbitrarilydistinguish between the elements such terms describe. Thus, these termsare not necessarily intended to indicate temporal or otherprioritization of such elements. The mere fact that certain measures arerecited in mutually different claims does not indicate that acombination of these measures cannot be used to advantage.

While certain features of the invention have been illustrated anddescribed herein, many modifications, substitutions, changes, andequivalents will now occur to those of ordinary skill in the art. It is,therefore, to be understood that the appended claims are intended tocover all such modifications and changes as fall within the true spiritof the invention.

I claim:
 1. A system comprising: a first switched-mode direct current todirect current (DC) converter that is arranged to selectively toggle afirst switch at a first switching rate; wherein the first switch iscoupled between a first power supply and energy storage components ofthe first DC to DC converter; a second switched-mode DC to DC converterthat is arranged to selectively toggle a second switch at a secondswitching rate; wherein the second switch is coupled between a secondpower supply and energy storage components of the second DC to DCconverter; wherein the second switching rate is higher by at least afactor of two than the first switching rate; wherein the first andsecond switched-mode DC to DC converters are mutually unsynchronized;wherein when the first and second DC to DC converters are coupled inparallel to each other to provide an output voltage; wherein the secondDC to DC converter is arranged to execute, per each cycle of operationof the second DC to DC converter: toggle the second switch at the secondswitching rate if at a certain point of the cycle of operation of thesecond DC to DC converter the output voltage is below a first voltagethreshold; and maintain the second switch open if at the certain pointof the cycle of operation of the second DC to DC converter the outputvoltage is above a second voltage threshold; wherein the first DC to DCconverter is arranged to execute, per each cycle of operation of thefirst DC to DC converter: toggle the first switch at the first switchingrate if at a certain point of the cycle of operation of the first DC toDC converter the output voltage is below a third voltage threshold; andmaintain the first switch open if at the certain point of the cycle ofoperation of the first DC to DC converter the output voltage is above aforth voltage threshold; wherein the first voltage threshold does notexceed the third voltage threshold.
 2. The system according to claim 1,wherein the second switching rate is higher by at least a factor of fourthan the first switching rate.
 3. The system according to claim 1,wherein the second switching rate is higher by at least a factor of fivethan the first switching rate.
 4. The system according to claim 1,wherein the first voltage threshold equals the second voltage threshold.5. The system according to claim 1, wherein the first voltage thresholddiffers from the second voltage threshold wherein the first DC to DCconverter is arranged to execute, per each cycle of operation of thefirst DC to DC converter: toggle the first switch at the first switchingrate if at a certain point of the cycle of operation of the first DC toDC converter the output voltage is below a third voltage threshold; andmaintain the first switch open if at the certain point of the cycle ofoperation of the first DC to DC converter the output voltage is above aforth voltage threshold; wherein the first voltage threshold does notexceed the third voltage threshold.
 6. The system according to claim 1wherein the first voltage threshold is lower than the third voltagethreshold.
 7. The system according to claim 1 wherein the first voltagethreshold equals the third voltage threshold.
 8. The system according toclaim 1 wherein the second voltage threshold is lower than the fourthvoltage threshold.
 9. The system according to claim 1 wherein the secondvoltage threshold equals the fourth voltage threshold.
 10. The systemaccording to claim 1, comprising a third switched-mode DC to DCconverter, wherein the third switched-mode DC to DC converter isarranged to selectively toggle a third switch at a third switching rate;wherein the third switch is coupled between a third power supply andthird energy storage components of the third DC to DC converter; whereinthe third switching rate is higher by at least a factor of two than thesecond switching rate; and wherein the first, second and thirdswitched-mode DC to DC converters are mutually unsynchronized.
 11. Amethod for providing an output voltage to a load, the method comprising:for each cycle of operation of a first switched mode direct current (DC)to DC converter: toggling a first switch at a first switching rateduring the cycle of operation of the first DC to DC converter if at acertain point in the cycle of operation of the first DC to DC converterthe output voltage is below a third voltage threshold; wherein the firstswitch is coupled between a first power supply and energy storagecomponents of the first DC to DC converter; maintaining, by the first DCto DC converter the first switch open if at the certain point in thecycle of operation of the first DC to DC converter the output voltage isabove a fourth voltage threshold; for each cycle of operation of asecond DC to DC converter: toggling a second switch at a secondswitching rate during the cycle of operation of the second DC to DCconverter if at a certain point in the cycle of operation of the secondDC to DC converter the output voltage is below a first voltagethreshold; wherein the second switch is coupled between a second powersupply and at least one energy storage components of the second DC to DCconverter; maintaining, by the second DC to DC converter the secondswitch open if at the certain point in the cycle of operation of thesecond DC to DC converter the output voltage is above a second voltagethreshold; wherein the second switching rate is higher by at least afactor of two than the first switching rate; and wherein the first andsecond switched-mode DC to DC converters are coupled in parallel to eachother and are mutually unsynchronized wherein when the first and secondDC to DC converters are coupled in parallel to each other to provide anoutput voltage; wherein the second DC to DC converter is arranged toexecute, per each cycle of operation of the second DC to DC converter:toggle the second switch at the second switching rate if at a certainpoint of the cycle of operation of the second DC to DC converter theoutput voltage is below a first voltage threshold; and maintain thesecond switch open if at the certain point of the cycle of operation ofthe second DC to DC converter the output voltage is above a secondvoltage threshold wherein the first DC to DC converter is arranged toexecute, per each cycle of operation of the first DC to DC converter:toggle the first switch at the first switching rate if at a certainpoint of the cycle of operation of the first DC to DC converter theoutput voltage is below a third voltage threshold; and maintain thefirst switch open if at the certain point of the cycle of operation ofthe first DC to DC converter the output voltage is above a forth voltagethreshold; wherein the first voltage threshold does not exceed the thirdvoltage threshold.
 12. A system comprising: a first direct current todirect current (DC) converter that is arranged to determine at a firstdetermination rate whether to alter a parameter of operation of thefirst DC to DC converter and to selectively alter the parameter ofoperation of operation of the first DC to DC converter in response tothe determination; a second switched-mode DC to DC converter that isarranged to determine at a second determination rate whether to alterthe parameter of operation of the second DC to DC converter and toselectively alter the parameter of operation of operation of the secondDC to DC converter in response to the determination; wherein the seconddetermination rate is higher by at least a factor of two than the firstdetermination rate; and wherein the first and second DC to DC convertersare mutually unsynchronized wherein when the first and second DC to DCconverters are coupled in parallel to each other to provide an outputvoltage; wherein the second DC to DC converter is arranged to execute,per each cycle of operation of the second DC to DC converter: toggle thesecond switch at the second switching rate if at a certain point of thecycle of operation of the second DC to DC converter the output voltageis below a first voltage threshold; and maintain the second switch openif a certain point of the cycle of operation of the second DC to DCconverter the output voltage is above a second voltage threshold whereinthe first DC to DC converter is arranged to execute, per each cycle ofoperation of the first DC to DC converter: toggle the first switch atthe first switching rate if at a certain point of the cycle of operationof the first DC to DC converter the output voltage is below a thirdvoltage threshold; and maintain the first switch open if at the certainpoint of the cycle of operation of the first DC to DC converter theoutput voltage is about a forth voltage threshold; wherein the firstvoltage threshold does not exceed the third voltage threshold.
 13. Thesystem according to claim 12 wherein the parameter of operation is aswitching rate.
 14. A method for providing an output voltage to a load,the method comprising: determining, by a first direct current (DC) to DCconverter, at a first determination rate whether to alter a parameter ofoperation of the first DC to DC converter; selectively altering theparameter of operation of operation of the first DC to DC converter inresponse to the determination; determining, by a second direct current(DC) to DC converter, at a second determination rate whether to alter aparameter of operation of the second DC to DC converter; selectivelyaltering the parameter of operation of operation of the second DC to DCconverter in response to the determination; wherein the seconddetermination rate is higher by at least a factor of two than the firstdetermination rate; and wherein the first and second DC to DC convertersare coupled in parallel to each other and are mutually unsynchronizedwherein the first and second DC to DC converters are coupled in parallelto each other to provide an output voltage; wherein the second DC to DCconverter is arranged to execute, per each cycle of operation of thesecond DC to DC converter: toggle the second switch at the secondswitching rate if at a certain point of the cycle of operation of thesecond DC to DC converter the output voltage is below a first voltagethreshold; and maintain the second switch open if at the certain pointof the cycle of operation of the second DC to DC converter the outputvoltage is above a second voltage threshold wherein the first DC to DCconverter is arranged to execute, per each cycle of operation of thefirst DC to DC converter: toggle the first switch at the first switchingrate if at a certain point of the cycle of operation of the first Dc toDC converter the output voltage is below a third voltage threshold; andmaintain the first switch open if at the certain point of the cycle ofoperation of the first DC to DC converter the output voltage is above aforth voltage threshold; wherein the first voltage threshold does notexceed the third voltage threshold.